1. Field of the Invention
The present invention relates to a method applied to an equalizer and related apparatus, and more particularly, to a method applied to an equalizer and related apparatus for reducing inter-symbol interference (ISI) by using a storage to store a training sequence component and a data component of an input data-stream during training the training sequence component.
2. Description of the Prior Art
Conventional digital television broadcasting formats include the Advanced Television Systems Committee (ATSC) format in the United States, the Digital Video Broadcasting-Terrestrial (DVB-T) format in Europe, and the Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) format in Japan. Due to multi-path channels existing during signal transmission, inter-symbol interference (ISI) is therefore generated. An adaptive equalizer, such as a decision feedback equalizer (DFE), is typically adopted in ATSC receivers for reducing ISI. However, a training sequence component of an ATSC signal is not long enough to guarantee operations of the adaptive equalizer. So a technique called data recycling is used for reusing the training sequence component of the ATSC signal for several times, thereby reducing convergence time of the adaptive equalizer.
Please refer to FIG. 1. FIG. 1 is a diagram showing a relationship table between input data-stream, channels, and coefficient of an equalizer according to the prior art. As shown in FIG. 1, Dt0, Dt1, and Dt2 respectively represent the input data-streams at time t0, t1, and t2. Ht0, Ht1, and Ht2 respectively represent the channels at the time t0, t1, and t2. Gt0, Gt1, and Gt2 respectively represent coefficients of an equalizer at the time t0, t1, and t2. In theory, the equations listed in the following should come into existence.Gt0×Ht0=1   (1)Gt1×Ht1=1   (2)Gt2×Ht2=1   (3)
However, it takes time to train the training sequence component of the input data-stream to be able to obtain the coefficients of the equalizer. For example, the training sequence component of the input data-stream Dt0 is trained at the time t0, and after a time interval (such as at the time t1) the coefficient of the equalizer Gt0 is obtained. At this time t1, if the coefficient of the equalizer Gt0 is used for reducing ISI of the current input data-stream Dt1, the equations above fail due to Ht0≠Ht1 and Gt0×Ht1≠1.
Such method called data recycling performs well in a static channel, which can effectively reduce the convergence time of the adaptive equalizer. But, if the channel is a dynamic channel or a mobile channel, which means the channel changes following with movements of users or alternations of environments (i.e., the channel is time-variant), coefficients obtained from conventional data recycling technology can't conform to practical situations. So conventional data recycling technology does not perform well and needs to be improved.